The proposed research plan is designed to prepare a novel fluorophore which will be attached to monoclonal antibodies and used as a cell surface antigen marker in flow cytometry. This marker can more easily be combined with other fluorophores for use in multiparameter flow cytometry than can the current alternatives. In addition, this fluorophore can be combined with DNA stains to obtain simultaneous cell surface and cell cycle information using the new, small, inexpensive HeCad or HeNe lasers. An inexpensive flow cytometer that could perform simultaneous cell surface and cell cycle analysis would be extremely useful in the field of tumor and AIDS diagnosis.